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Masters Theses 1911 - February 2014

1937 A review of the pests of ,: with a detailed study of the biology of the native elm bark (Hylurgopinus rufipes Eich) William Bernard Becker University of Massachusetts Amherst

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Becker, William Bernard, "A review of the insect pests of elm,: with a detailed study of the biology of the native elm (Hylurgopinus rufipes Eich)" (1937). Masters Theses 1911 - February 2014. 1307. Retrieved from https://scholarworks.umass.edu/theses/1307

This thesis is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Masters Theses 1911 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. a moyiKw (m 'HiE pBiH pests of elm, WFlH A DETAILED STUD'V OF BiOLOGY §f THE NATIVE ELM BARK BEETLE, KYUJKCOPINUS RUF1PES E1CH,

BECKER - 1937

[ Mor LD 3?34 M268 193?

' B3968

cop . 2 J DATE DUE

UNIVERSITY OF MASSACHUSETTS LIBRARY MORR LD 3234 M268 1937 B3968 cop. 2 with a Detailed A Review of the Insect Pests of Elm, Study of the Biology of the Native Elm Bark Beetle, Hylurgopinus ruf ipes Eich.

By

William B. Becker

Graduate School Thesis to the Faculty of the Submitted as a Requirement for the In Partial Fulfillment of the Degree of Master of Science Massachusetts State college

June 1937 CONTENTS

Page

Introduction 1

Importance of

Importance of attacking Elms 6

Recorded Insect Pests of Elm 8

Relation of Bark 3eetles to Fungous Diseases 17

Hylurgopinus rufipes Eich 19 Description and Synonoray * 19 Recorded Host Plants ..*. 19 Distribution 20 Relationship to the Dutcn Elm Disease 20 Methods and Technique 22 Studies of Adults 22 Hibernating Adults 22 Spring Emergence 22 Summer Emergence * 22 Studies of Eggs 24 Studies of Larvae 24 Studies of Pupae 24 Studies of Parasites 25 Records of the Physical Environment 25 Studies of Host Materials 25 Life History and Habits • 25 Host Preference 25 Hibernation 26 Adult Hibernation 27 Larval Hibernation Brood Galleries • Egg Galleries 33 Larval Galleries 35 Adult Emergence 36 Activities after Emergence • 38 Reproductive Potential 40 Associated • 41

Summary 45

Conclusions • 48 Or Bibliography 49 CO cr>

««# ca CD ZD ITS. INTRODUCTION

The purpose of this study is to gain a better knowledge of

the life history and habits of the native elm bark beetle,

Hylurgopinus rufipes Eich*, in order to determine the proba-

bility of it becoming an important vector of Ceratostomella

ulmi, the causal organism of the * Little

information has been available regarding the life history and habits of this beetle which, before the introduction of the

Dutch elm disease, was considered of only secondary importance

because it was not known to attack healthy trees* Now that the

Dutch elm disease is established on this continent, the beetle

comes under suspicion as a possible vector, for it breeds in

weakened and recently killed elms, some of which may harbor

Ceratostomella ulmi in localities where the Dutch elm disease

exists, later attacking other elms for feeding and egg-laying

purposes* In fact, when its habits are compared with those

of the closely related but introduced European elm bark beetle,

Scolytus multistriatus Marsh*, which make it the most important

vector of the disease in this country, the two are found to be

similar. multistriatus ha3 been associated with

Ceratostomella ulmi in Europe for a number of years and the

relationship between them has been studied extensively. The

native only came in contact, with the disease after the

latter was Introduced into this country about 1930 and the

relationship has not been studied to the same extent. However, .

it has been shown experimentally that adults of Hylurgopinus ruf lpes from diseased elms can carry the spores, and the has been recovered from the new galleries made by those in previously non-infected logs (Collins, Buchanan,

Whitten, and Hoffman, 1936; Britton, 1935; Clinton and

Mccormick, 1935) IMPORTANCE OF ELiJS

There are six species of elms indigenous to the United

States which attain tree size. Three of these are of first

importance as ornamentals or producers of lumber. They are

the American or Shite Elm ( Ulmus amerlcana Linn.), the Red or

Slippery Elm (U. fulva Michaux), and the Rock or Cork Elm

(JJ. raceinosa Thomas). The other three native species are of

minor importance and occur in the South. These are the r/inged

2lm (M* alata Michaux), Cedar Elm (U. crasslfolla Nuttall), and

Red or September Elm (U» serotina Sargent). In addition,

several other species of elms have been introduced into this

country from abroad.

The natural distribution of the six native species is

outlined by Sudworth (1927) as follows:

" Ulmus amerlcana Linn. From southern Newfoundland to Lake Superior (north shore) and to the eastern base of the Rocky Mountains (here up the Saskatchewan River to latitude 54° 30"); south to Florida (Desoto County); west to North Dakota (Turtle Mountains), South Dakota (Black Hills), western Nebraska, central Kansas, Oklahoma, southwestern Arkansas (Rich fountain), and Texas (coke County).

w Ulmus racemosa Thomas. From Quebec (eastern townships) throu;n Ontario, and south through northwestern New Hampshire to southern Vermont; and to northern New Jersey; westward through northern New York; southern Michigan, central Wisconsin (Lake Mendota, near Madison), and southwestern Minnesota to north- eastern Nebraska (Meadville), western Missouri, eastern Kansas, and middle Tennessee.

" Ulmus fulva Michaux. From Lower St. Lawrence River (Orleans Island) through Ontario to South Dakota and eastern Nebraska, southeastern Kansas, southwestern Arkansas, and •

Oklahoma; south to western Florida, central Alabama, and Mississippi, western Louisiana and Texas (Kerr and Comal Counties)

ififhaux. From southern Virginia Florida"BSKn to central (Lake County), and from southern Illinois and through Indiana western Kentucky and Tennessee to the Gulf, through and west southern Missouri, Arkansas, eastern Oklahoma, and Texas (Guadaloupa River).

"MiS. crassifolia Nuttall. From Mississippi (sunflower River) througn southern Arkansas and Texas (from coast to the Pecos River) to Mexico (Huevo Leon).

"Ul£]H£ serotina Sargent. Range imperfectly known at present; known now, at different stations, only from southern Kentucky and Tennessee to northeastern Georgia, northern Alabama, northwestern and southwestern Arkansas and eastern Oklahoma; southern Illinois (Richland County)."

The most important of the native elms is the American elm,

Ulama amerlcana . It has been planted extensively over its

natural range and has been introduced onto the west coast as

an ornamental shade tree. People prefer it over many other

shade trees because of its deliquescent form which throws a

moderate shade over the ground, yet leaves enough space beneath

its branches for free movements of air and traffic. It also

permits the suburban type of home with peaked roof to be erected

beneath the arches formed by branches of adjacent elms. Because

of these and other characteristics of growth and adaptability to

street, park and lawn planting, Fernow (Herrick,1935) rates it

as one of the most valuable of the common shade trees in the country.

Numerous shade tree authorities and literary people praise

our elms, many pointing out the beauty of elm-shaded New England villages and historical elms scattered over the country. some .

Barraclough (1935) persons place a monetary value on them. limits in New valuates the estimated 100,000 elms within town that 50,000 Hampshire at |3,000,000. Curtis May (1934) says represent elms in only five cities in northern New Jersey and real thousands of dollars invested in planting, care, calls the American elm estate values- Michaux (Illick,1924) the Temperate Zone. One toe most magnificent "vegetable" of visualizing the may realize the importance of our elms by This fact is appearance of the country stripped of them. and Michigan, where especially true of New England, New York, their best growth (Mul ford, 1926) the elms are said to attain IiSPORTANCE OF INSECTS ATTACKING ELHS

highest in Although the American elm ia ranked among the twentieth by Howard in shade tree value by Fernow, it is placed trees rated on the basis of a list of twenty-six common shade rating is 1.25. resistance to insect attack. Its valuated to insect attack are Those trees showing the highest resistance least resistance to insect given a rating of 3.0; those showing The low resistance attack are rated at 0.10 (Herrick.1955) . insect-borne plant disease like of elms favors the spread of an feeding Insects may defoliate an the Dutch elm disease. Leaf and thereby reduce its vitality elm for a few consecutive years insects may attack it. Information so that wood and bark-boring date suggests that elm available on the Dutch elm disease to of the disease. A study of bark beetles are the chief vectors this is possible. their bark homing habits shows why of each individual species The breeding and feeding habits importance as a vector of a disease. of insect determines its contact considered are the degree of Among the factors to be portions of the tree, the the insect has with the diseased to needed for toe insect's attack condition of toe host which is attacks the tree, toe number of occur, toe manner in which it toe abundance of the insect, generations produced each year, on both the physical and biotic environment and therffect of toe essential point causina the disease. An insect and the organism insects as estimating the importance of to be considered when causal organism vectors of disease is: to what extent can the other possible agents of the disease be spread by the wind and the insects? It should of dissemination without the help of emerge from a diseased be remembered that when the insects are substituting the tree and attack a healthy tree, they innoculation method for the direct and highly successful wound When the fungous «hit and miss" wind dispersal method. of a sticky nature and organism which causes a plant disease is tree, extent, on exposed portions of the i 3 not produced, to any enable it to be spread easily and a condition which would not must depend upon agents which profusely by the wind, the fungus plants. for transmission to other do come in contact with it Cerates tome 11a ulmi, U at present The Dutch elm disease fungus, The habits of elm bark considered to be of this nature. are contaminated with the fungus beetles are such that when they other elms with the fungus. they can successfully innoculate trees always been associated with Elm bark beetles have not so a study of the relation- infected with Ceratostomella ulmi valuable. the disease may prove ships of other insects to attack diseased portions of the Since other wood-borning insects the spread as possible factors in trees, they should bo regarded coleoptera, especially true of the of the disease. This is larval and woody tissues in both the many of which attack the considered leaf-feeding forms are not adult stages. The disease. probable vectors of the RECORDED INSECT PESTS OF ELM

mi tee Numerous insects of various orders and several the elms. A attack elms. A few species are peculiar to of trees with equal vigor. large number attack several families however, are only The vast majority recorded from elms, rare. Following occasional pests, many of the latter being to attack elms in America. It is a list of species known pests and most of thos. includes all the economically important this list, one may get an which are unimportant or rare. From of insects which have been idea of the many and varied types associated with elm recorded from elms. Insects and mites and predators nave been pasts as scavengers, parasites, grouped according to the type omitted. The pests have been individual species are listed under of injury produced. The

the order to which they belong. pests of elm are noted The economically important abundant and cause local outbreaks Those which are occasionally unimportant and rare are merely are noted *. Those wnich are listed by their scientific names. » . .

— 9 —

woody parts of elms. I. Insects attacking

A. Boring insects. Coleoptera Alaus oculatus L» TTTEhaxia viridicomis say "~ X. viridifrona Gory oicornis"""Web. Boatriclius' Buprestis rvif ipes Ql iv Catogenus rufua Fabr Chrysobo'Ehris femorata Oliv. Cuc'ujua c lavipea Fabr. pendrophaaus cygnaei Mann. Dicerca divarlcata Say Dorcas parallelus Say pryopxua aexfasciatus Say pularius brevillneus Say Eburea quadrigeminat.a Say EgHogonlu s aubarnatul Lee gupsalis roinuta Dru. Goes pul'verulentus Hald. HTster lecontei Mars. H. parallelus Say ** Hylurgoiinus rurfpjs Eichh. I~v illo sus Fabr. Hyp ermal"" Ieptura q5ar'pinata Fabr. Ty^axyTon sericeiim Harr. ir* Stalls armlcollis Say «# mT barblta Hay Micracis langatani Blackm. Sb narCErua mali Fitch* • Neoclyius"acuminatus Fabr. « capraea Say N. egproceohalus Fabr. |. acutellaris Oliv* t)berea_ tripunctaia awederus » ^cTcIeres cingulatus Say 0^ texanus Horn, ^sjaoderma eremlcola_ Knoch- Horn " frtidooe'pfialua cj^vrglatil Parandra brunnea F* PhloeopHagus minor Horn. Phyliooius objlongus L. physocnemum brayiXlneum Say pllt/ynna c'ompo situs Gay Sapsr^lateransFabr ~" »» siT trldent.ata Oliv. Say S» veatita. n

— 10 -

Scolytus multl3triat.u3 Marsh. S. sulcatus Lec« Stenoscelis breyTs Boh. Synchro a punctata M ewma TenebroTdes cortical is Melsh* Trichodesma glbbosa Say Uliota dubTus Fabr. Xyloterlnua politus Say Xylotrechus colonus Fabr. Ligyrus gTSboaus DeG» (Root feeder) polycruaua impress ifrons Gyll- (Root feeder)

Lepidoptera

prionoxys tus robiniae Peck. Z mazer a aesculi L« «•* 2« pyrina L»

Hymenoptera

Tremex columba L« C amponotus herculearms v1ar» pennsylvanicus DeG.

Isoptera Retlculitemes flavipea Kollar

Diptera

Ctainophora apicata O.S. Ollgarces ulmi Felt

B. sucking Insects Homoptera

Suale Insects Aspidiotus ancylus Putn. Comst. A . perniclosus * X. ulrai Johnson *K Qhionaapis americana Johnson Coccus citricola comp. Eulecaaium canadenss Ckll. E» caryae Fitch. nigrofasciatum Perg f . «e Gosayparia "spuria tjodeer. * Lecanium corni Bouche Lepidosaphea ulmi L» a a

— 11 —

&ytllaspi8 porno rum 3ouche Pnenacoccus aoerlcola King (Also called a mealy bug) Pseudaonidia dupl ox Ckll. Pulvinaria ianumarabllls Rathvon P» vitis L. Aphida

griosoma crataegl Qeatland f* pyrlcola" 3a«er & Davidson ** E. rlleyi Thomas ** Lougiatlgma caryae Harr.

Heraiptera

Lop idea heldemann Kngt. Lygos Invitus Say

C» Injury produced by ovipoaltion habits. Homoptera

* BBS63 bubalus Fabr. Tibicea ctliaromera walk, f • llnnal Smith & Groasbeck Orthoptera

Hap i thus agitator uhler Qecantnua niveua~Servllle

II. Insecta and mi tea attacking the leaves of alma.

A> Chewing Insecta

Ab bo tana clementarla Abb. & Sm. ** Also;jhiTa pometarla Harr. Apatela anerlcana Harr. A« funeral is Gr. & Rob. X. grlsea Walk. ^. impleta Walk. A* interrupta Guen. A* morula Grt. X. occidental i G« & R. X. ul.nl HafrU X» vinnula Grt. . .

— 12 -

Archlps argyrosplla Walk. A. raaana L» Argyresthia auateralla zellar Automeria £o Fabr. Bactra ? "argutana Clem. fasTTarchia arthemis Dru. Baailona laperalla Drury Bbmolocha aballsnalia Walk. Cacoecia^ar- yrospila Walk Canaraia ulmi arro ao'rel la Clara. CeratomTa amyntor Fmbn. Charadra^d'er1 dens Guen. pa tana con tract a Walk qI miniatra Dru. pellephlla Uneata Fabr. peiopeia bslla L« Kacleg imperial la Drury Edama "al bifrons A*bb. & Cm. Ennomos ma^narTua Guen. # f: aubalgnarius Hubn. gplrritsjdilutata Huon. gpi 3 imus argutanua Clem. Irannls " 'tiliaria narr. Eu choeca alblfera Walk. "Fuclaa chloria H»~ & S» julieTtriferana Walk. fm^Eroma dlvarallinaata Hx'bn. fTTcarTa blllneata Pack. r.li^hisla septentrional ia Walk. ~" qZ trillneaia t^actc. G"raptolitha laj.icifiarea Grote Halisidota caryae Harr. S« A« H~- tesasTlarla & Hamadrya3 antlc-pa L'- tfamarocampa definlta Pack. S* h A- ** H~* leucoatlgma Heterocampa billneata""Pack. HTbernia tiliaria Harr. fl-ul3tea undulatell a Clem. HypercKiria io. Fabr. iHt Hyphantr fa~cunga Drury Harria I c n ihyxtra" "am a r1 cana La^oa crlapata Pack. LlHenltia artnemla Drury Lochmoeua sp. Lophodanis trifaranua Walk, tiycia co^natarla Guen. irSTacgaoma americana Fabr. Hubn. f; disatria . .

— 13 —

Mesoleuca intermediate Guen. Metanema querclvorarla Guen. iietrocampa prae-randaria Guen. fte-honteryx ? ulmi-arrosorella Clemens NT undul aTella Clemens We rice bldenta^a Walk. Hygmla phaeorrhoea Don. ^ene 'plagiata 7aTk. er-i boreata Hubn. Qpheropt " ** Paleocr ita ye*fnata_ Peck. Paoniaa excaecatus Abb. & Sm. para phi a unipuncta Haw.

, cbior is H»3« parorgyla cilntonii G« & R* Percnapt flota fiuvlata Hubn. Petropho ra divers iilneata Hubn. yhlgalia jitea Cram. rlatysamla eecropia Linn. " po lygonla comma Harr. p. lnterro^ationl3 Fabr. progne Cramer «# porthetria diapar Linn. S an i a c ecro p la L 1 nn j}T plover! fitrecker tichizrura concinna S. & A«

Coleoptera Brachys aeroaa tjels. g. bvata Vsber Chrysomela multifiuttata Stal. Lee c . scalaris p t cue Say ?To no tr achelu s anaf-ty i notalpa lanigera Linn. CrvptoTe^halus quadru,;lex Newm. plcteXonycha elongate Fabr. Galeruc'a calmariensls L» — 14 —

**• Galerucella luteola Mull* Grap todera carinata Germ. HaiUca cHalybea Illiger *- #1 ' ulml noodle Macro da ctylus subsplnosus Fabr. « Monocesta coryli r*ay Phloeqpkiagus minor Horn.

el. 1* ft*) fusca Fro §* inversa Horn. (T j Lee (L.) nltlda £• rugosa gelsh. Plaglodera versicolor La itch, ^locetej^ulffll Lee. polydrusvia im press ifrons Gyll* w poplllia "Japonica Mewnan Systena marginal is 111- Xantho'ni a decemnotata say

Hymenoptera

** cimbex americana Leach

Orthopter* nla pheromera femorata Say

plecoptera

pailfda""3anks f. and mites. B. sucking Insects Homoptera

Aphids Callipterus elegant Koch. ^ * ** sp. sanborn •£* ulmicola Thos. «« colopha uJ^micoT^Tnch Sriosoma americana Riley * JanT^fum Hausm. «ft T- Hartig f . lanuginosa ca hoTtes & Frison f . ilml * £. ulrai Linn. feorgia uTmpnison Lachnus platani Kalt. L« ' ulm - Linn. »

-- 15 —

i,lyzocailis ulnifolii Monell Pemphigus ulmi Llchi. pT"^ ulmifuaus -?alsh. p. wal3hl will lama "schlzoneura compresaa Koch, fetraneura alba RatzT # ifl grarninis Laonell ^. pail i da ~peGuer t. rubra Licht- %t ulqi DeGeer Patch f . ulalaaccull

Scales Chlonaspls americana Johnson Coccus citricol*i Cornp* Gossyparia spuria J'odeer Lecmlu.r, corn! Bouche phena coccus acaricola King Also called mealy bugs Phenacoccus daarnessl King ^Tso" called mealy bugs Paeudaonldla duplex CkH» pu lvinA'ria" Trmonierauilis Rathvon. f, vltls Linn.~~ Aleyrodids

Aleurodea esslgl Penny.

Leaf hoppers and tree hoppers

Empoa rosae Linn. EryiKroneura ador tlcAtee Tvohlocvba cymba jdcAtee J- ^rTcTncta Fitch ffi/ Fulgorid

r-oeclloptera prulnosa Say

Hemiptera

Lygus Invitua Say ir& Corythucha ulmi Oab. & ur.

Acarina (Mites)

Pa ratetranychus pilosus C & F» fenui palpu s '/other a 1 McGregor Tetranycnus aim3culatus Harvey — 16 —

insecta and mites. C. Leaf mining and gall forming Leaf mining insects Lepidoptera coleophora limosipennella Drury Ll ihocoITotos -,r -antlnotella Clem. f£ " ulmella chamb*

Coleoptsra Odontota nervosa Panz. Orcueste's pallicornls Hay

Hymenoptera

«# Kallofenusa ulmi Hund. ~;ylotoma scapularis Klug*

Diptera Agromyza ulmi fjund.

Gall formers Acarina (Mites)

# Erlophyes_ sp« Siebold £• ulmi Garraan

Cause blasted and aborted buds Diptera

Dasyneura u line a Felt phy topha'ga ulj^i -Seutm.

i RELATION OF BARK BEETLES TO FUNGOUS DISEASES

Several elm bark beetles of the Scolytidae are considered vectors of the Dutch elm disease in Europe. These include Scolytus mnl tistriatus Harsh* a Scolyt ;s scolytus Fab.,

- Scolytus pygmaeus Fab . , Scolytus laevla Chap . , Scolytus solci frons Rey., Scolytus af finis Egg., Hyle sinus vittatus Fab., and Hylesinus kraatzi Eich. Scolytus multistriatus is the only one of these pests established in the United States.

This species and Hylurgopinus ruf ipes Eich., the native elm bark beetle, are the only abundant bark beetles of elms in

America. Both are known to be capable of infecting elm wood with the fungus which causes the disease (Collins, Buchanan,

Whitten, and Hoffman, 1936).

A knowledge of the relationship between bark beetles and fungi is not new. Beetles of the genera Dendroctonus and are associated with the spread of blues tain fungi. These fungi, which belong to the same as that producing the

Dutcii elm disease, cause large annual losses in the lumber industry, due to the staining of the affected wood.

Ambrosia beetles of the family Scolytidae dig long tunnels through the sapwood and heartwood of a tree and depend upon the growth of certain fungi in the tunnels for their food supply.

They do not eat the tissues of the wood but feed entirely upon the fungus. The spores of these fungi cling to the bodies of the beetles and are transported from tha old to the new galleries where they germinate in "gardens* and develop the

••ambrosia" or food of the beetles. .

— 18 —

In every ca3e the transmission of the fungus is purely mechanical. The insects concerned come in contact with the casual organism of the disease at an early period of their life cycle when they attack the same parts of the plant wnich the or fungus attacks. The fungus spores adhere to their bodies Later, when get into their digestive tracts while feeding. or egg-laying the insects attack other plants for feeding into the purposes, the spores of the fungus are introduced affected by the tissues of the plant and cause it to become

fungus HYLURGOPINUS RUFIPF3 BICH.

The only native elm scolytid known to be abundant in this

country is Hylurgoplnus rufipes , commonly known as the native elm bark beetle. A review of literature revealed very little information on the life history and habits of this bark beetle before 1935. Th6 earlier articles appear to be records of casual observations or, at the most, very incomplete observa- tions of its life history. Recent papers (3ri tton,1935;

Collins»3uchanan»Vihit,ten,and Hoffman, 1936; Herrick,1935;

UcDaniel,1935; Becker, 1935) give a more complete record of the life history, but much yet remains to be done.

Description and Synonomy

Eichhoff (1868) originally described the insect as

Hylaste s rufipes . Later in the same year, LeConte (1868)

described it under the name Hylesinus opaculus . Both names have been applied to the beetle in literature since then. which Swaine (1918) established a new genus, Hylurgopinus , of

H* ruf ipes is the only species.

Recorded Host Plants

The species is chiefly an elm pest. It has been reported

however, on soft maples (Devereaux,1831), basswood (Swains, 1918 . ,

— 20 —

Herrick,1935; Pierson, 1927) , tamarack (Harrington, 1884)

arbor vitae (Lintner,1387), ash (Perkins, 1890; Packard, 1890;

McDaniel,1935; Lintner,1381), and cedar (r.wenk, 1909)

Distribution

Worthley (1935) reports that H. ruf ipes has been collected

throughout most of the northern range of the American elm.

Various atithors have reported specimens found in Maine, New

Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island,

New York, New Jersey, Pennsylvania, Del revere, Maryland,

••Carolina," Virginia, West Virginia, Kentucky, Ohio, Indiana,

Missouri, Kansas, Michigan, "The Middle states," and in eastern

Canada.

Relationship to the Dutch Elm Disease

Hylurgopinus ruf ipes Sleh« has habits almost identical

with those of the introduced European elm bark beetle, Scolytus

multlstrlatus Harsh.

In the case of an infected tree in Old Lyme, Connecticut,

no evidence of Scolytus multlstrlatus was discovered. Instead,

Hylurgopinus ruf lpe3 was present in abundance. Ceratostomella

ulrai was cultured from the adults which emerged from this tree.

Some of these adults were allowed to attach healthy elm twigs under controlled conditions. subsequent cultures of these — 21 -

and twigs showed the presence of the fungus (Clinton other elms in the Mccormick, 1935). The following year several were stricken with the vicinity of the originally infected tree

Dutch elm disease. of the confirmed Readio (1935) reports that 67.4 percent Scolytus riulti- infestations of caratoatoaella contained contained tridentata, and 10.9 striatus . 54.4 percent

percent contained Hylurgopinus rufipee. bark- infesting Transmission experiments with several Dutch Elm Disease Laboratory insects have been carried on at tne With the exception of Scolytus at ilorristown. New Jersey. the results of all multistrlatus and Hvlurgopinus rufipes, authors say that occasional experiments were negative. The other insects, but these positive cultures were obtained with error" in the studies. were probably due to "experimental and Hoffman, 1936) (Collins, Buchanan, Whitten, muiti- report, that 7 out of 19 Scolytus C V7. Hay (1935) had the field In diseased areas 8tri3 tu S adults taken In their bodies, but only 1 out neratostomella ulmi cultured from presence The rufipes adults snowed its of 7 F. ylursoplnus experiment was not carried out author adds, however, that the this work is the same extent. When on Hvlurgoplnus rufipes to different. done, the results may be Methods and Technique

Studies of Adults

Hibernating Adul ts . The outer layers of bark were

stripped from parts of the trunks of American elm trees ( Ulraus amerlcana ) and the adults observed in their hibernating tunnels*

Spring Emergence . The beetles* activities durin^ the spring period of flight were followed by making observations daily between three and four p. If. in a grove of elms in which adults were abundant the previous winter. Freshly cut elm logs were placed in the grove to attract the beetles for ovi- position purposes* Because of the small size and obscure color of the beetles, white cheese cloth was 'trapped around the trunks of several trees and logs in order to distinguish them more easily whenever they should crawl or fly about. The air

temperature was recorded at the time of each observation so that a correlation could be made between it and the beetles' activi-

ties.

When the trap logs were attacked, the bark surfaces were

closely examined for evidence of the beetles* activities.

Aft?r they had dug beneath the surface of the bark, strips of

bark were removed and placed between two pieces of glass to

observe the construction of the egg galleries on the inner

surface of the bark.

Sunnier Emergence . 7/hen pupae were found beneath the bark,

sections of elm logs were caged to catch the adults on emergence. — 23 —

The logs were waxed on both ends to conserve moisture and placed in large glass cylinders measuring twelve inches in diameter. The ends of the cylinders were covered with thin voile cloth and secured with thick rubber bands and twine.

The cylinders were laid horizontally to permit free circula- tion of air. They were in the moderate shade thrown by the surrounding elms.

For supplementary rearing purposes glass cylinders, standard wire-mesh rearing cages, and large battery jars were used in the laboratory. Soil was ;»laced in the bottom of each and regularly watered In order to moisten the logs which were placed vertically in this soil at the bottom of

the cages and jars. The top ends of these logs were waxed

to conserve the moisture in them.

The newly emerged generation of adults from the caged material was collected by using a suction bottle. The suction bottle consists of a small bottle with two glass-tipped rubber

tubes inserted through a two-holed rubber stopper. The end of one tube is placed in the worker's mouth and the other is placed over one of the tiny beetles. suction through one tube draws the beetle into the bottle through the other tube. A

tiny piece of wire-mesh screen clued to the bottle end of the

tube leading to the operator 1 s moutii prevents the beetles from entering the mouth. Then counts are made the cloth is removed

from a jar and the beetles rapidly collected in the suction

bottle. This method is possible because the beetles are usually slow to take flight. 24 —

Studies of Eggs .

Strips of bark were removed from logs and examined microscopically to study tne eggs in the galleries.

Studies of Larvae .

After egg galleries were started in the trap log3,

development within the bark was observed periodically by

removing a strip of bark from a log and counting the larvae present and measuring the widths of their heads to determine

approximately tne stage of larval development (Dyar,1890).

Mature larvae which had stopped feeding and were ready to pupate could be distinguished from the immature ones during

their active season because they -#ere entirely white in color,

no food being visible through the body wall as with Immature,

feeding larvae.

Studies of Pupae .

Mature larvae were removed from the bark and placed in

glass vials suspended by a string inside a bottle having a salt

solution with an excess of the salt at the bottom to keep the

humidity of the air In the bottle constant. The bottle ?;as

kept at room temperatures. In this way, the time at which the

larvae changed to pupae, and the length of the pupal stage, were

noted, as well as the length of time it took for the young

adults to attain their natural color. — 25 —

Studies of Parasites .

The cocoons of parasites in the bar* sere removed and reared to adults in a jar like that used to rear the hoat.

Records of the physical Environment .

All temperatures were taken with a mercury thermometer and recorded in degrees Fahrenheit. The bulb of the thermo- meter was shaded during observations.

Studies of Host Materials .

The American elm Culmus americana ) was used entirely a3 host material for all the life history experiments in the fi6ld and laboratory, since it was the only host upon which the beetles were found locally. Other species of elm were not available for experimental purposes at the time. Logs of tr^es oth^r than alms were used in one experiment to determine if the beetles would breed in them also.

Life History and Habits

Host Preference .

An attempt was made to determine if beetles which are bred in elm logs can produce another generation of beetles in bass-

is al30 reported to be a host wood ( Tilla glabra ) % a tree Wiiich soma beetles were of Hylurgoplnus ruflpas . £n the expsriment, confined on elm, some were confined on basswood, and others were given their choice between elm and basswood. The results of the experiment are shown in the following table.

Jar Number of Number Type of Wood Beetles Results

Baaswood 80 Very few bark punctures. No egg galleries made

Basswood 50 Basswood - very few bark

and Elm punctures • Mo egg galleries made.

Elm 80 Numerous bark punctures. Egg galleries made.

It is evident from the table that basswood is unattractive to beetles reared in elm under the conditions of the experiment.

Hibernation .

KylurgopinU3 ruf ipes was observed to pass the winter in bo tii the larval and ad'ilt forms in Amherst, Massacnusetts.

The adults passed t^e winter in short bark tunnels in the

trunks of live trees. Larv«e of both the first and second generations passed the winter in trap logs. Of the first generation there were merely a straggling few which had had

their development stopped by the cold weather in the Fall before tney could become adults and emerge with the rest of their gener- ation. Those of the second generation -sere quite abundant.

The eggs from which they developed were laid In late August and in September (Chart III). ~ 27 —

1934 and 1935 the first Adult Hibernation. In both latter part of adults were observed in the bark tunnels in the similar to fine, September, when a considerable amount of dust bark crevices mixed brown and white sawdust was noticed in the State of several American aim trees on the Massachusetts probably due to College campus. The two colors of dust were which are found in the alternate light and dark layers of bark tunnels into this species of elm. The beetles were digging tunnels (Fig. 1) the bark of apparently healthy elms. The pattern such as were snort and not constructed in any regular Moreover, egg they dig when making egg galleries (Fig. 2)- and recently galleries, as shown later, are confined «o dying the crevices of killed material. All entrance holes were in outer bark, bark and most of the winter tunnels were in the the sapwood but many were in the inner bark, some scoring spot about one- slightly. The following spring a small brown surrounding fourth inch in diameter was noticed in the sapwood November 1934 the spots where the beetles scored it. By 5. season. A few, most of the beetles had stopped boring for the From time to however, showed signs of Uft «"en disturbed. were examined and time during the winter, trie infested trees (Chart HI). live beetles observed in a dormant condition exposure to room During the coldest weather some require.}

temperatures for an hour before they revived. Some were There were many abandoned tunnels In the bark. forcing them to filled with sap which repelled the beetles, - 28 -

Figure 1 n^t«r lavara of bark have been stripped

One-iialf naturui aize Figure 2 Hylurgoglroia Characteristic egg gallery of £H£^ of American elm ^uiraus Eich. beneath the bark americana ) Natural size — 30 —

withdraw and start tunnels elsewnere. Frequently the abandoned tunnels were occupied by other small forms of many life. During the latter part of the winter were adults died in their tunnels. Many of these beetles so enveloped in a white fungous growth resembling that tunnels. commonly seen on dead bark beetles within their were on the The greatest number of the bark tunnels several being in trunks of the trees near the ground level, tree forked near the the bark of exposed roots. Where a the crotches showed a ground, the rougher and thicker bark in smoother bark sur- greater infestation than the thinner and less abundant faces on the trunk. The infestation was

toward the upper part of the trunk. the most heavily infested It was interesting to note that elm logs which trees were near a log pile containing many from seasons past. showed old egg galleries of H. rufipes parent beetles which These galleries contained only the dead construct. commonly die in the egg galleries they throughout the entire The bark tunnels were examined Observations were made daily period of adult occupation. Fall and the period of during the period of attack in the Durin, mid-winter, examina- renewed activity in the Spring. three week intervals. tions were made only at ab.ut sequence of activities in these A table showing the

tunnels follows: . .

Maximum Air Date Activity Temperature

Sept. 29, 1934 Adults in abundance attacking 70 trunks of live elms.

Nov. 5, 1934 Most of the adults in the 66 tunnels had stopped digging for the season.

Dec. 15, 1934 All beetles in tunnels now dormant. No signs of life when disturbed. Required one hour of exposure to room temperatures to revive

Jan. 18, 1935 Still dormant. 34

Marcu 16, 1935 A few beetles showed signs of 68 life when disturbed.

April 19, 1935 First boring dust found in crevices 64 of the bark, showing that beetles renewed digging in their tunnels.

April 27, 1935 Beetles actively digging in tunnels. 86 Boring dust very abundant in crevices of bark.

May 11, 1935 First beetles crawling about on the 65 bark.

May 13, 1935 First adults observed flying and 73 landing on tree trunks.

May 20, 1935 Egg galleries started in elm logs 68 which were exposed to attract the beetles

* All temperatures were taken from the Massachusetts State College Experiment Station weather reports. and the The relationships between the beetles' activities WQre air temperatures durin - the sprinn period of flignt observed to be as follows;

Fahr. and above Flylng 66 degrees and above Crawling on bark only 60 degrees Fahr. Fahr. and above Digging in tunnels only 55 degrees

bark of At no time were egg galleries seen in the egg healthy trees, as were the winter tunnels. As the in the spring, galleries became mora numerous in the trap logs in the living fewer beetles were found in the bark tunnels

trees.

larvae were not seen Larval Hibernation . Hibernating only fifteen almost until the second winter (1935-36) when were found in logs in mature larvae of the first generation live adults were found at one of the field jars. Five young which they had not yet the ends of larval galleries from belonged to the same gener- emerged. These larvae and adults emerged. The cold ation as the beetles which had already development and activity. weather had apparently arrested their ^e field at Similar examinations made on otnor logs pMPi * produced similar results. A few the same time in the spring that the entire brood had of these logs, however, showed .

already emerged. No live pupae were found among the few individuals which were collected in the field during the winter (Chart III).

In August 1936 trap logs were placed in the field.

Adults of the first generation which emerged at this time con- structed egg galleries in these logs and produced a second generation whic, over-wintered as larvae (Chart III).

Brood Gallerie s

Sgg Galleries . The beetles first attacked freshly cut elm logs in the latter part of May (May 20) and started con- structing egg tunnels beneath the bark (Chart III). One beetle, presumably the female, would start the hole (Garraan,

1899) while another beetle, presumably the male, would take a position directly behind it. Then annoyed with a blade of grass, the male would move about as if to protect the female.

When the female tunneled below the surface, the male would stand just outside the hole, sometimes partially covering it with his body. Later, when the hole was deep enough, the male entered an:l remained in the entrance, its elytral declevity effectively blocking the opening against enemies. By carefully cutting away the bark beside the tunnel and covering it with celluloid, some of the activities within could be observed.

The female bored directly into the sapwood andthen across the grain of the inner bark, slightly scaring the sapwood. The male usually remained near the entrance uole, but sometimes was found in a side niche in the section of the tunnel between the .

mm 34

male's role seemed to be entrance hole and the sapwood. The presence at the entrance hole that of guardian, in that its female digging below, and prevented enemies from attacking the helped remove boring dust pushed also that of janitor, as it operation was performed with back to it by the female. This laid its eggs in the the tibia and tarsi. The female the grain of the inner branches of the tunnel which ran across in tiny niches dug into bark. These eggs were laid singly as they extended both sides of each branch of the tunnel Each egg was covered with through the tissues of the bark. female produced as she dug closely-packed boring dust which the

the tunnel observed until three weeks Subsequent development was not the log and placed between later when bark was removed from and previously described under "Methods two pieces of glass, as to the egg gallery at Technique." There were two branches eggs female was digging and laying that time. Sometimes the hole. was still near the entrance in one branch while the male and the male female would be in one branch A t other times the parent beetles remained alive in would be in the other. Many part of July when the first their galleries until the latter of larval galleries beneath young adults were found at the ends of previous to this time. In most the bark. Some had died present only one dead beetle was the egg galleries observed, This habit is quite after the gallery was completed. scolytids. The male usually characteristic of other species of well started. leaves after the egg gallery is — 35 —

characteristically consists of The completed egg gallery opposite directions from the two branches whicn extend in inner bark. Under entrance hole across the grain of the galleries vary sligutly crowded conditions, however, these beetle's efforts to avoid from this shape, because of the some have a »V« breaking through to a neighboring tunnel. in almost any shape, the two branches of which extend bark. None has been direction in relation to the grain of the parallel to the grain. found, nowever, with both branches on, branch extending Sometimes an egg gallery will have only but a vestige of n second aore or less across the grain with The total lengths of the branch in which there are no eggs. 1.5 cm. to 6.0 cm. They were egg galleries varied from about about 1.5 mm. wide.

hatch from the eggs Larval Galleries. The larvae *h*«b gallery at approxi- begin digging away from tne parent egg which hatch first from the mately right angles. Those larvae larvae continue to ear.ier-laid eggs and the faster digging As the larvae grow, the extend their tunnels at this angle. later-developing larvae to bear galleries widen and force the started digging sooner, until away from their neighbors which last laid eggs will curve those larvae developing from the they are digging in the same their galleries so that finally gallery, unless they are cut off direction as their parent egg by neighboring galleries. entirely from further development — 36 -

the inner bark next The younc larvae usually burrow In when the bark is removed. to the sapwood, and are exposed cambial region and dig wholly The older larvae often leave the therefore not exposed to view within the inner bark and are few nay remain next to when the bark is torn off. However, a

the sapwood. were found (Chart III). On July 12 the first pupae the galleries. The Pupation takes place at the ends of six to eight days, in the pupation period usually lasted from adults are a very pale experiments. The newly transformed shade the larvae. They soon tan in color, almost the same « h the bark, and emerge become darker, bore outward thrcu C Some bore aimlessly through holes about one mm. in diameter. emerging. A few of these about in the inner bark before

latter perish without emerging.

Adult Baergence . period several logs Immediately preceding the emergence and cut to 20 inches in between 4 and 9 inches in diameter cylinders placed in a hori- length were placed in six glass were taken from two infeated log zontal position. These logs located in a cool, shady gully piles. One pile (No. 1) was of the (No. 2) wan at the top beside a stream; the other pile to daily temperature was from one gully near a field where the on sunny days. Bach pile three degrees Fahrenheit higher piled on the ground. The consisted of three layers of logs

— 37 —

were between individual logs were about four feet, long and piles were about four and nine inches in diameter. The log

five feet long. which the logs were The ends of the glass cylinders in cylinder contained wood placed were covered with voile. One contained wood from from the top log in one pile; a second contained sections of each the bottom of the pile; the third cylinders were similarly log in the pile. The other three

prepared with wood from the second pile. from both the log pile Adult emergence began July 30 th the warmer location, and ten and the logs in the cylinders in cooler location (Chart III). days later from those in the both piles, the daily fluct- After emergence was under way in in the two locations was uations in the amount of emergence However, the greatest almost identical throughout the season. warmer location was attained emergence from the log pile in the emergence from toe log pile in on August 20th, while maximum on September 11th. Charts the cooler location was attained logs in emergence from sections of all I and II show the daily average curve using three day both log piles based on a moving

periods. taken fro™ the tops of the Beatl.s emerged M the logs from the logs taken from th. pilea e few days earlier than produced In the lowest logs wm bottom, but the total number shown the same sise. Tnls ie larger than in the top logs of

in the following table: — 38 —

Number Emerged Date of First Emergence Total _Too Bottom Log Pile Top Bottom 1.947 2.108 1 Aug. 9 Aug. 13 1.408 2.214 2 July 28 July 30

Activities after Emergence .

beetles were not observed to In the field, the adult as reported by Britton attack Mis for feeding purposes, when confined with twigs in cages. (1935). They did, however, from elm emergence of Hylurgopinus rufi£es Soon after a heavy Llassachusetts, the beetles logs in Amherst and in vyestfield, tunnels into the trunks of Were seen digging short bark These tunnels are of apparently healthy American elm trees- they spend the winter. In the same type as those in which durin, the second week in Westfield, the attack was noticed was not noticed until the August. in Amherst, this attack end of August (Chart III). A following year (1936) near the short trees showed the presence of close examination of several parts of branches even in the upper bark tunnels in trunks and approximately crotches of some small branches, tii e trees. The of bark over, snowed the presence one inch in diameter and decidedly branches, however, there were tunnels. In the smaller the ground area than in the trunk near fewer tunnels per unit of twigs feeding was found, even where level. No case of twig bark trunk w.ich showed numerous lay against a part of the — 39 —

tunnels. This habit seems to differ slightly from tint of the young adults of Scolytus multi3triatus which are reported to attack small elm twigs and buds. Only when Hylurgopinu3 ruf ipes adults were confined on small elm twigs In the field and laboratory did they attack them. 'ihsnever they had a choice between small twigs and stouter elm material, they did not attack the twigs.

At about the time the bark tunnels were noticed in the trees in Amherst, egg galleries were constructed in nearby trap logs, and a second generation started which is wintering in the larval stage (Chart III). Numerous bark tunnels were also in the trap logs.

In the Fall of 1934, 1935, and 1936 the trunks of elms were attacked by Hylurgopinus ruf ipns adults. Repeated exami- nations during these winters showed the presonce of live adults

in tunnels in the bark of these trees.

A summary of the complete activities of Hylurgopinus

ruf ipes as described in the previous pages of this section on

"Life History and Habits" is shown in graphic form in Ch.- rt

III.

.

Reproductive potential

Although the egg galleries are two-branched, the species is reported to be monogamous (Swains, 1913) . No readily

visible method of differentiating the sexes was known when

this work was done, but my observations tended to bear out

his findings. r/hen bark was stripped from logs, never more

than two beetles were found in a gallery, one of which was near tue entrance hole, the other in one of the branches.

Sometimes one would bo in each branch. In many, only one adult was found, the second being absent, as often is the case with male bark beetles. In the Spring of 1935 I carefully

transferred the two adults from each of four newly-3tarted egg galleries in the field to a caged log in the laboratory. Four e ZE galleries were made, each with the characteristic forked tunnel. The behavior of the individuals in a gallery was

Characteristic of the behavior of the male and female of other monogamous scolytids. Only one dead parent beetle remained in each gallery when it was completed.

The number of eggs found in a series of egg galleries which were? examined varied considerably. In a few galleries both parents died before any egg3 were laid. In some galleries botL parents died after only six or eight eggs were laid.

Finding between twenty and eighty eggs to a gallery was quite common. The maximum number of eggs found in one egg gallery was one hundred and twenty-four. McDaniel (1935) reports that a female lays from twenty to seventy-five eggs in a brood tunnel — 41 —

A table comparing the number of egg galleries with the

total number of first generation adults which emerged, follows.

This table also shows the average number of progeny produced from one egg gallery.

Total Adult Number of Egg Average Number of Emergence Galleries Adults Emerged per Gallery

2,132 172 12.39

1,947 119 16.36

Total 4,079 . 291 14.017

Since an average of only fourteen individuals were

secured from 291 galleries, tnere would seem to be a heavy

mortality among the immature stages. This may have been due

to the crowded condition of the larvae in the logs under

observation. The f aster-growing larvae crowd out the slower,

and thus prevent their further growth in many cases. Parasites

and possibly predators might take their toll, and the physical

environment must also cause some mortality.

Associated Arthropods

Several kinds of insects and other Arthropods are

associated with the various life stages of Hylurgoplnus ruf ipes ,

or with the galleries in which they live. Below is a list of

these Arthropods, supplemented by a short account of the

activities observed. - 42 —

INSECTA

Collembola .

These nere on the trunks of elm, in the winter galleries and in the egg galleries in the field, and were numerous in the rearing jars. A list of the species follows:

Qrchesella cincta L.

Isotonic cinorea il\c.

To mo c ems vulgaris Tull.

Sira buekl Lubb.

Coleoptera .

T*he galleries of a few other wood-boring insect3 were often intermingled with those of H. ruf ipes » These included:

Scolytus mul tistriatus idarsii.

IJagdalis spp.

Saperda tridenta ta 01 iv.

Saperda tridentata was most commonly found in samples collected from all parts of the state. They attack elm bark about the same time as Hylurgapinus ruf ipes but require until the following spring to emerge as adults, whereas practically all of the American bark beetles on elm emerge the same season that development started, if the eggs from which they developed were laid in the spring. The galleries of Saperda tridentata are long, winding and broad, and practically obliterated the gallery patterns of Hylurgjpinus ruf ipes by the end of the first summer. . . i

43 —

coarctatum Lee, was found in A small beetle, ^jsoma

ruflpes . abandoned winter tunnels of Hylurfiopinus sap which flowed from Two beetles were attracted to the ruflpaa in the trunk of a a tunnel made by Hvlurgoplnua They were: healthy tree during the early spring. Euphoria inda L. Scarabaeadae Glischrochilus fasclatus Oliv. Kitudulidae beetle, (1893) reports that a Clerid A . D . Hopkins on Hylurgop inus rufioes. Thanasimus dublus, is predaceous

Diptera . larvae were occasionally Tiny undetermined dipterous

found in the egg galleries.

Hymenoptera . Hymenopterous insect *as occasionally A tiny cocoon of a larval gallery. A drlad found at the and of an unfinished mflpes .as always attacu ed to tha larval skin of Hvlurgopinus iluesebeck or predatis*. Doctor cocoon, suggesting parasitise identified the species as national i3useum of to. united Statas an family Braconidae. It ie Spatnlus canadensis Ashrcead, beetles of several species of oar* insect recorded as a parasite srandi- Phloeoslnus dentatus. r.ay, Ipa and .eevils, including Dr^coetes aHsrlcanus Hopk. coilis Flch. (Leonard. 1926); sraniser Chap. (Pierce.1908) Toaicus caco^ra^hus. Phloeoslnus and gardens olvra Host, a-olrtu. rugulosus Ratz. t«**l.*»»>l

(pierce, 1908) 44 —

ARACHNIDA

Aranlda .

Several tiny undetermined species of spiders were found in abandoned winter tunnels. Some spider e^gs were found in tne egg and larval galleries of Hylurgoplnu3 ruf lpes .

Acarina .

Mites were numerous in egg and larval galleries. "?hen sections of beetle-infested bark were examined microscopically they were readily seen crawling about in the tunnel 3. An undetermined species of mite was seen on the bodies of adult beetles, apparently doing no harm. SUMMARY

Hibernating Habits young In the vicinity of Amherst, iiassachuaetts, may pass Hvlurgoplnua rufipea adults of the first Generation in the bark of the winter in short tunnels which they dig slightly apparently healthy elms. Sometimes the sapwosd is almost mature larvae scored. A very small percentage of generation may over- and also some young adults of this same which they develop. winter in larval galleries in the logs in

pring and Summer Activity winter in the over- The young adults which had passed the the third week in wintering tunnels resumed digging in them began constructing egg April. They left these tunnels and These beetles galleries in elm logs near tae end of L'ay. until the middle of July. remained alive in their egg galleries gallery they construct. Either one or both parents die in the e C,a the eggs laid by the The young larvae which hatch from the egg gallery, dig parent female in niches along the side of through the inner bark and away from the parent egg gallery construct. The pupate at the ends of the galleries they kno-n as larval galleries. galleries the larvae construct are of they dig out to the surface <*h«n tne pupae become adults, galleries. Each beetle leaves the bark and emerge from their in diameter. a tiny hole about one millimeter — 46 —

Adult emergence begins about the end of July and emergence continues until past Vie middle of October, most individuals taking place during August and September. A few in the larval of the same generation may pass the winter to feed upon stage. Young adult beetles were not observed They elm twigs in nature, as reported by Britton (1035). into the trunks were found, however, to dig short bark tunnels August soon after a and branches of apparently healthy elms in twigs were heavy emergence from nearby elm logs. The small started at about not touched in nature. A second generation larval stage. this same U«h, passing the winter in the

Host preference americana) was the only species of American elm ( Ulmus at the time this work elm available for experimental purposes in rearing a new was done. The beetles were successful their attack. generation in it wnenever it was exposed to was not chosen for breeding purposes Basswood ( Tilia glabra ) Various authors cite it by adults which were reared in elm.

as being a host of tue beetle.

Reproductive potential to lay between Although it is common for tne beetles as one hundred twenty-four, twenty and eighty eggs, and as high reaching the adult stage was only the average number of beetles experiments. fourteen per egg gallery, in the 47 —

Associated Arthropods which is Spatnlus canadensis Ashmead, a Braconid, species of bark beetles reported to be a parasite of several Hylurgopinus ruffes also. and weevils, was found to parasitize were associated with the Several insects, spiders and mites galleries they make. beetles themselves, or with the

Compared ruflpea are similar to The ooring habits of Hylurgopinus ilarsh., the only other elm those of scolytua multistriatus in this country. Scolytus bark beetle present in abundance the most important multistriatus is today considered to be America. Because of this vector of the Dutch elm disease in snould also fa regarded with fact, Hvlur^opinus rufipes this problem was started, suspicion in thia respect. Since experiments, that Hvlurgo- several authors nave found, through spreading Ceratostomella ulmi, the plnue rufipes is capable of elm disease (Co 11 ins, Buchanan. causal organism of the Dutch ***** Britton,nritton LV&oi1935- ****Clinton and LlcCormick, Written, and Hoffmann, 1036,

1935) • CONCLUSIONS

and a partial second 1. There is one complete generation vicinity of Amherst, generation in a single season in the

Massacuusetts. recently ruflpes breeds in the bark of 2 . H ylurgoplrma tunnels in the bark of killed elm wood. The adults later di 8 the sapwood slightly. They thrifty elms, sometimes scoring of recently killed elm wood to may go directly to the banc beetles, or they may spend the start another generation of bark of the healthy tree. This winter in the tunnel in the that of scolyjius multi a triads life cycle is very similar to

Marsh. bred in eln «U* not breed in 3. The beetles rchich ere to be e noat of besseood. wnien ie eiao reported g&SM3*Bg

rufipes . .

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W° r y in the United States. ^5 ' D^tch £2 d^ease eradication Jour. Scon. Ent. 23:524. ACKNOWLEDGEMENTS

Sincere thanks are due to Professor H. L. Sweetman for his helpful suggestions and his constructive criticism of the manuscript. Professors A* V. Osraun and L. L.

Blundell offered useful advice in the composition of the Statio thesis. The Massacnusetts Agricultural Experiment kindly permitted the use of photographs. The author is Folsom for also indebted to tne late Doctor Justus *« Mr. C. A Frost for identification of collembola, and to •

identification of Coleoptera. Approved By-

May 1937 i M II